Various methods have been proposed, in which a heat dissipation member is embedded in a printed board in order to dissipate heat generated in electronic components mounted on the printed board.
For example, in JP-A-2010-258260, an opening portion (through-hole) is provided on a position on the printed board where the electronic components are mounted, and the heat dissipation member (via conductor) of which the area is smaller than that of the opening portion is fitted into the opening portion. In addition, in an inner circumferential surface of the opening portion, a plurality of grooves is formed in a circumferential direction in a predetermined interval, and a plurality of protrusions engaging with each groove is formed on an outer circumferential surface of the heat dissipation member. Furthermore, a gap generated when the heat dissipation member is fitted into the opening portion is filled with a filling material made from an adhesive resin, and thus, the heat dissipation member is fixed to the printed board.
In addition, in JP-A-2010-205995, an opening portion (a through hole that passes through the printed board) is provided on a position on the printed board where the electronic components are mounted, a heat dissipation member (a metal piece) is inserted into the opening portion, and then, by deforming the heat dissipation member by pressurization, the heat dissipation member is fixed to the printed board and the height of the printed board and the height of the heat dissipation member become the same. In addition, protruding and recess portions are provided on the inner circumferential surface of the opening portion, and an apex of the protruding portion is made to be in contact with the heat dissipation member, and then, a gap between the opening portion and the heat dissipation member is filled with solder.
As in JP-A-2010-258260 and JP-A-2010-205995, when the protruding portion or the recess portion is provided on the inner circumferential surface of the opening portion or on the outer circumferential surface of the heat dissipation member, and the inner circumferential surface of the opening portion and the outer circumferential surface of the heat dissipation member are made to be in partial contact with each other, it is possible to prevent the heat dissipation member from getting out from the opening portion.
In addition, in JP-A-2014-157949, a through-hole provided on a lower base member is filled with a metal sheet or metal paste, a metal pattern is printed thereon, then, an upper base member is laminated and pressurized, and then, the metal base heat dissipation member (a heat-transfer member) is embedded into the base member. On the upper side of the heat dissipation member, a plurality of wiring patterns is provided via an insulator and electronic components are mounted on each wiring pattern.
As disclosed in JP-A-2014-157949, when a plurality of electronic components are mounted on the upper side of one heat dissipation member, it is possible to effectively dissipate the heat generated in the plurality of electronic components using the heat dissipation member and it is possible to improve a mounting density of the board.
On the other hand, in a multilayer printed board, for example, as disclosed in JP-A-2003-17862, an insulation layer and a conductive layer of the base member are formed from a double-sided wiring board and prepreg. By the prepreg being sandwiched between the plurality of double-sided wiring boards, and the plurality of double-sided wiring boards being heated and pressurized, a thermosetting resin contained in the prepreg is dissolved, and then, the thermosetting resin is cured. Then, the plurality of double-sided wiring boards and the prepreg are integrated.